/*
 * 版权所有：义乌市路比信息科技有限公司
 * 作者：kinwyb<http://www.lcfgly.com>
 * 日期：2015-12-1
 */
package lcfgly.utils;

import lcfgly.exception.LRunException;

/**
 * 生成唯一号
 * URL:http://www.cppblog.com/tx7do/archive/2014/06/10/207248.html
 * @author kinwyb<http://www.lcfgly.com>
 * @datetime 2015-12-1 14:33:53
 * @version 1.0
 */
public class IdWorker {

    private final long workerId;
    private final static long twepoch = 1361753741828L;
    private long sequence = 0L;
    private final static long workerIdBits = 4L;
    public final static long maxWorkerId = -1L ^ -1L << workerIdBits;
    private final static long sequenceBits = 10L;
    private final static long workerIdShift = sequenceBits;
    private final static long timestampLeftShift = sequenceBits + workerIdBits;
    public final static long sequenceMask = -1L ^ -1L << sequenceBits;
    private long lastTimestamp = -1L;

    public IdWorker(final long workerId) {
        super();
        if (workerId > IdWorker.maxWorkerId || workerId < 0) {
            throw new IllegalArgumentException(String.format("worker Id can't be greater than %d or less than 0", IdWorker.maxWorkerId));
        }
        this.workerId = workerId;
    }

    public synchronized long nextId() {
        long timestamp = this.timeGen();
        if (this.lastTimestamp == timestamp) {
            this.sequence = (this.sequence + 1) & IdWorker.sequenceMask;
            if (this.sequence == 0) {
//                System.out.println("###########" + sequenceMask);
                timestamp = this.tilNextMillis(this.lastTimestamp);
            }
        } else {
            this.sequence = 0;
        }
        if (timestamp < this.lastTimestamp) {
            throw  new LRunException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", this.lastTimestamp - timestamp));
        }
        this.lastTimestamp = timestamp;
        long nextId = ((timestamp - twepoch << timestampLeftShift))
                | (this.workerId << IdWorker.workerIdShift) | (this.sequence);
        return nextId;
    }

    private long tilNextMillis(final long lastTimestamp) {
        long timestamp = this.timeGen();
        while (timestamp <= lastTimestamp) {
            timestamp = this.timeGen();
        }
        return timestamp;
    }

    private long timeGen() {
        return System.currentTimeMillis();
    }
}
